2,199,999,999,978 & 4,399,999,999,956 & 8,799,999,999,912

[Math.]

(*)   8712 = 2178×4 & 8712×2178 = 18,974,736 = 43562

87128712 = 21782178×4 & 87128712×21782178 = 435643562

(**)   87912 = 21978×4 & 21978×87912 = 1,932,129,936 = 439562

8791287912 = 21978…21978×4 & 21978…21978×87912…87912 = 43956…439562

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(***)   8,799,999,999,912 = 2,199,999,999,978×4 &

2,199,999,999,978×8,799,999,999,912 = 4,399,999,999,9562

8799...99128799...9912 = 2199...99782199...9978×4 &

2199...99782199...9978×8799...99128799...9912 = 4399...99564399...99562

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(****)   879…912 = 219…978×4 & 219…978×879…912 = 439…9562

879…912879…912 = 219…978…219…978×4 &

219…978219…978×879...912…879...912 = 439…956439…9562.

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2,404,879,675,441

[Math.]  Euler numbers (or secant numbers) are defined by the infinite series: sec(x) = 1/cos(x) = 1+E2(x2/2!)+E4(x4/4!)+E6(x6/6!)+…, where E0 = 1, E2 = –1, E4 = 5, E6 =  –61, E8 = 1,385, E10 = –50,521, E12 = 2,702,765, E14 = –199,360,981, E16 = 19,391,512,145, E18 = –2,404,879,675,441…

The odd-indexed Euler numbers are all 0. The even-indexed Euler numbers have alternating signs.

2,999,999,999,996

[Math.]

296×333,667 = 98,765,432

2,996×33,336,667 = 99,876,654,332

29,996×3,333,366,667 = 99,987,666,543,332

299,996×333,333,666,667 = 99,998,766,665,433,332

2,999,996×33,333,336,666,667 = 99,999,876,666,654,333,332

29,999,996×3,333,333,366,666,667 = 99,999,987,666,666,543,333,332

299,999,996×333,333,333,666,666,667 = 99,999,998,766,666,665,433,333,332

2,999,999,996×33,333,333,336,666,666,667 = 99,999,999,876,666,666,654,333,333,332

29,999,999,996×3,333,333,333,366,666,666,667 =

= 99,999,999,998,766,666,666,663,333,333,332

299,999,999,996×333,333,333,333,366,666,666,667 =

= 99,999,999,998,766,666,666,665,433,333,333,332

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